This invention relates to a method and means of encasing long slender objects such as nuclear fuel rods for shipment and handling.
Nuclear fuel rods, especially those that have been removed from a nuclear reactor, present a technical challenge when it is desired to remove them from one location to another. The fuel rods are slender and spent fuel rods are made brittle by exposure to radiation. Spent fuel rods emit radiation and may be heated enough by the presence of radioactive fission products to need cooling for shipment. They must be separated from each other to permit the circulation of coolant and to protect them from damage by rubbing against each other or the shipping container.
Present practice for shipping spent fuel rods involves first inserting the spent rods into metal tubing and supporting the tubing in a geometrically spaced arrangement in a shipping cask. The geometrical arrangement facilitates the circulation of a coolant about the rods and the tubing provides structural support for rods that are typically slender enough to be whippy and are in addition embrittled from radiation when they have been in a nuclear reactor. Spent rods can only be thus inserted in tubing in a hot cell which protects operators from dangerous radiation. When a spent rod is warped or bowed, it becomes difficult to insert the rod into a metal tube and it is necessary in any event to use a tube that is enough oversize to permit the insertion of a rod that exhibits typical distortion. This is especially true if the rod must be inserted by remote means in a hot cell. In addition, the tendency apparent in present reactor development is that fuel rods seem to become increasingly slender and increasingly long. For example, fuel rods for the EBR-II reactor, located at the west facility of the Argonne National Laboratory at the Idaho National Engineering Laboratory, range in diameter from 3/16 inch to 1/4 inch and are of the order of 5 feet long. Fuel rods for the Fast Flux Test Facility (FFTF) are 94 inches in length with diameters of the same order as those of the EBR-II. Such rods need protection on shipment whether spent or not and the method of protection must be feasible for use with spent rods that exhibit some physical distortion.
It is an object of the present invention to provide a better method and means of encasing nuclear fuel rods for shipment.
It is a further object of the present invention to provide a better method and means of encasing nuclear fuel rods in tubular containers.
It is a further object of the present invention to provide a better method and means of encasing distorted spent nuclear fuel rods for insertion into a shipping cask.
Other objects will become apparent in the course of a detailed description of the invention.